1. Field of the Invention
The present invention relates to an elastic transformable body for adjusting vapor pressure, a vapor pressure adjustment chamber using the same, an ink-jet recording head having a vapor pressure adjustment device and an ink-jet recording device having the recording head, and more particularly to a vapor pressure adjustment device for adjusting negative pressure generated in a liquid chamber in an ink-jet recording head when discharging ink.
2. Related Background Art
Among recording methods such a printer, the ink-jet recording method to form text or image on a recording medium by discharging ink from a discharging hole (a nozzle) is a non-impact recording method, which enables high-speed recording with high density, so being broadly applied.
A general ink-jet recording device includes an ink-jet recording head, a means for driving a carriage having the ink-jet recording head, a means for carrying the recording medium, and a controller for controlling the driving means. Such an operation to perform recording with moving the carriage is called as a serial type. On the other hand, the manner of performing recording only with carrying a recording medium without moving the recording head is called as a line type. In the line-type ink-jet recording device, the ink-jet recording head has a plurality of nozzles arranged to a width of the recording medium along overall width.
Because discharging ink drop from the nozzles, the ink-jet recording head includes an energy generating means to generate discharging energy exerted to the ink in the nozzles. As the energy generating means, there are used ones of using an electric-mechanical converting element such as piezo element, using electric-thermal converting element such as a heating resistance, or using an electronic wave-mechanical converting element or an electronic wave-thermal converting element for converting electronic wave into mechanical vibration or heat such as an electronic wave laser. Among them, the manner of discharging ink drops by using the thermal energy may arrange the nozzle in very high density, so enabling recording in high resolution. Particularly, the ink-jet recording head using the electric-thermal converting element as the energy generating element is more easily scaled down rather than the one using the electric-mechanical converting element, and furthermore when adapting an IC technique or micro-processing technique with technical advance and improved reliability in the recent semiconductor making field to fully utilize their benefits, there are also advantages of high density, easy mounting and lowered manufacturing costs.
As for supplying the ink to the ink-jet recording head, there are a so-called head tank integrated manner in which an ink tank containing the ink is integrated with the ink-jet recording head, a so-called tube supplying manner in which the ink tank is connected to the ink-jet recording head through a tube, and a so-called pit-in manner in which the ink tank is independently installed to the ink-jet recording head, moving the ink-jet recording head to the ink tank to connect them as required, and then supplying the ink from the ink tank to the ink-jet recording head therebetween.
If increasing capacity of the ink tank to reduce frequency of changing the ink tank, the weight of ink tank is also increased, which is not preferred in the head-tank integrated manner of the serial-type ink-jet recording device, considering that the load exerted on the carriage is increased. Therefore, the serial-type ink-jet recording device using the mass capacity ink tank usually adopts the tube supplying manner or the pit-in manner. Among them, since the pit-in manner requires stopping the recording process during supplying the ink, the tube supplying manner which may operate in longer time is better adopted.
An ink supplying system of the tube supplying type ink-jet recording device is described below with reference to FIGS. 10A and 10B.
The ink supplying system shown in FIGS. 10A and 10B includes a main tank 304 containing ink 309 therein, a supply unit 305 detachably mounted to the main tank 304, and a recording head connected through a supply tube 306 to the supply unit 305.
The supply unit 305 has an ink chamber 305f therein. The ink chamber 305f is opened by an atmosphere hole 305g and at the same time connected to the supply tube 306 through a bottom of the ink chamber 305f. The supply unit 305 also has hollow ink supply needles 305a of which lower ends are positioned in the ink chamber 305f and upper ends are protruded from an upper surface of the supply unit 305, and the lower ends of the hollow ink supply needles 305a are positioned lower than lower ends of atmosphere introduction needles 305b. 
The ink tank 304 has at a bottom two connectors having a rubber stopper to seal the main tank 304, and has an independent sealed structure with the main tank 304. When mounting the main tank 304 to the supply unit 305, the ink supply needles 305a and the atmosphere introduction needles 305b are respectively inserted in the main tank 304 through the connectors. Since positions of the lower ends of the ink supply needles 305a and the atmosphere introduction needles 305b are set as above, the ink in the main tank 304 is supplied to the ink chamber 305f through the ink supply needles 305a, and the atmosphere is introduced in the main tank 304 through the atmosphere introduction needles 305b to supplement the pressure decrease in the main tank 304. If the ink is supplied in the ink chamber 305f up to the level that a lower end of the atmosphere introduction needles 305b are soaked in the ink, the atmosphere is not introduced in the main tank 304 so that supplying ink from the ink tank 304 to the ink chamber 305f is stopped.
The recording head 301 has a sub tank 301b for accumulating a constant amount of ink as an ink container, an ink discharging unit 301g in which a plurality of nozzles for discharging ink are arranged, and a flow channel 301f connecting the sub tank 301b to the ink discharging unit 301g. In the ink discharging unit 301g, the nozzle has an open channel downward and the ink is discharged downward. In each nozzle of the ink discharging unit 301g, the above-described energy generating means is installed. The sub tank 301b is positioned above the ink discharging unit 301g, the supply tube 306 is positioned above the ink discharging unit 301g, and the supply tube 306 is connected to the sub tank 301b. Between the sub tank 301b and a flow channel 301f, there is attached a filter 301c having a fine mesh structure to prevent the nozzle from plugging caused from that minute impurities in the ink are infiltrated into the ink discharging unit 301g. 
An area of the filter 301c is set to regulate pressure loss less than an allowance value. The pressure loss at the filter 301c is increased as the mesh of the filter 301c is finer and as a flow rate of the ink passing the filter 301c is larger. On the contrary, the area of the filter 301c is in inverse proportion. The recent recording head of multi-nozzle and small head tends to increase the pressure loss, so the size of the filter 301c is made as larger as possible to restrain the increase of pressure loss.
On an upper surface of the recording head 301, installed is an elastic member 321 having an appearance of an approximate rectangular shape in order to form a pressure adjustment chamber 322 for adjusting pressure in the sub tank 301b by absorbing abrupt change of pressure in the sub tank 301b. The pressure adjustment chamber 322 is connected only into the sub tank 301 through an opening 301d formed on an upper wall of the recording head 301. As the elastic member 321 transforms according to the pressure change in the sub tank 301b, volume of the pressure adjustment chamber 322 changes to absorb the pressure change of the sub tank 301b. A shape of a section of the elastic member 321 in parallel to an upper surface of the recording head 301 has a size nearly equal to or less than the upper surface of the recording head 301. In such a reason, a certain height is required to obtain a required volume of the pressure adjustment chamber 322.
Because the nozzle of the ink discharging unit 301g is open to the atmosphere and the opening is toward lower direction, the inner of the recording head 301 is required to maintain negative pressure in order to prevent the ink from leaking from the nozzle. On the other hand, if the negative pressure is too large, air is infiltrated into the nozzle so making it impossible to discharge ink from the nozzle. Therefore, in order to maintain suitable negative pressure in the recording head 301, the recording head 301 is arranged so that the opening of the nozzle is positioned higher as much as a height H than a liquid surface of the ink in the ink chamber 305f, so maintaining the inner of the recording head 301 to the negative pressure of a water head difference value of the height H. As a result, the nozzle is maintained to be fully filled with the ink with forming a meniscus on the opening.
The ink is discharged from the nozzle by pressing out the ink in the nozzle with use of driving force of the energy generating means. After discharging the ink, the nozzle is filled with ink by the capillary force. The processes of discharging ink from the nozzle and filling the nozzle with ink are repeated, and the ink is sucked in from the ink chamber 305f through the supply tube 306.
If the ink in the ink chamber 305f is sucked up to the recording head 301 so that the liquid surface of the ink in the ink chamber 305f is lower than a lower end of the atmosphere introduction needle 305b, the atmosphere is introduced in the main tank 304 through the atmosphere introduction needle, the ink in the main tank 304 is therefore supplied to the ink chamber 305f, and then the lower end of the atmosphere introduction needle 305b is soaked again into the ink of the ink chamber 305f, With repeating such operations, the ink in the main tank 304 is supplied to the recording head 301 according to discharging of ink from the recording head 301.
By the way, in the sub tank 301b of the recording head 301, the air infiltrated by permeation of resin materials such as the supply tube 306 or the air dissolved in the ink are gradually accumulated. In order to discharge the residual air accumulated in the sub tank 301b, the sub tank 301b is connected to an exhaust tube 301a connected to an exhaust pump 301c. But, as described above, a valve 310b is installed to the exhaust tube 310a in order to maintain suitable negative pressure in the recording head 301. The recording head 301 is regulated not to be into the atmosphere pressure by opening the valve 310b only when discharging the air.
In addition, in case that the ink discharging unit 301g is clogged with thickening things of the ink or the residual air dissolved in the ink is accumulated and saturated in the ink discharging unit 301g, a recovery unit 307 is generaly installed to the ink-jet recording device to eliminate the air. The recovery unit 307 includes a cap 307a for capping the nozzle opening of the recording head 301 and a suction pump 307c connected to the cap 307a, and eliminates (removes) thickening things of ink or residual bubbles from the ink discharging unit 301g by driving the suction pump 307c with the nozzle opening being capped with the cap 307a, and then compulsorily sucking out the ink in the recording head 301.
In this suction-recovery operation, since thickening things and residual bubbles are more effectively eliminated as a flow rate of the ink is faster, the flow channel 301f has a small size of cross section in order to make the flow rate of the ink faster in the flow channel 301f. On the other hand, because the cross section of the filter 301c is set as big as possible, the flow channel is formed so that the cross section is decreased below the filter 301c. 
Though the conventional ink supply system is so far described with an example of the tube supplying manner, the structure below the filter of the recording head in the head integrated manner and the pit-in manner is also basically identical to that of the tube supply manner, only that the structure for supplying ink from the ink tank to the recording tank is different.
On the other hand, in the general color ink-jet recording device, color is formed on the recording medium by subtractive color mixing using cyan ink, magenta ink and yellow ink. Moreover, in order to increase color development of the image, inks for improving gradation such as black ink, light cyan ink, light magenta ink, and light yellow ink and inks for broadening color reproduction such as red ink, green ink, blue ink, orange ink and violet ink are used. Therefore, the ink-jet recording head has an one-color ink drop discharging unit for one head, or, in case of color, a multi-color ink drop discharging unit for one head, and this head is loaded on the ink-jet recording device to realize color printing. Therefore, if the recording head 301 shown in FIG. 10 is for color, the ink discharging units 301g, the flow channels 301f, the sub tanks 301b and the pressure adjustment chambers 322 respectively in the number corresponding to the number of ink colors are installed in the recording head 301 in series.
However, in case of attaching the elastic member 321 to install the pressure adjustment chamber 322 for the sub tank 301b to the recording head 301 like the ink supply system shown in FIG. 10, the elastic member 321 preferably has a rectangular shape to obtain capacity of the elastic member 321 to the maximum. But, since surfaces of the rectangular shape is not fully regular when the inner pressure of the elastic member 321 becomes negative pressure, the elastic member 321 is not transformed to a stable shape. As a result, because the transformed shape of the elastic member 321 irregularly changes, the relation between the reduced air volume in the elastic member 321 and the negative pressure in the pressure adjustment chamber 322 becomes unstable.
In addition, as another problem of the rectangular elastic member 321, there is a phenomenon that the elastic member 321 is interfered with adjacent elastic member 321 when being pressed.
Therefore, an object of the present invention is to provide, in a pressure adjustment chamber using an elastic transformable member mounted for adjusting vapor pressure in a vessel, an elastic member compacted and using the function of the pressure adjustment chamber to the full with a simple structure and low costs, and a compact ink-jet recording head having the pressure adjustment chamber using the elastic member, and an ink-jet recording device having the recording head.
Thus, in order to accomplish the object, the present invention provides a pressure adjustment chamber having at least one elastic transformation body having a changeable volume according to vapor pressure to adjust the vapor pressure in a container communicated thereto and a support for supporting the elastic transformation body to the container,
wherein the elastic transformation body includes an approximately circular opening and two surfaces approximately flat before transformation at an outer circumference, in which the two surfaces have a shape extended through a curved portion at a front end opposite to the opening.
In one aspect, the present invention features a pressure adjustment device having a chamber through which vapor enters and exits, at least one elastic transformation body having a changeable volume according to vapor pressure to adjust the vapor pressure communicated with the chamber and a support for supporting the elastic transformation body to the container, wherein the elastic transformation body includes an approximately circular opening and two surfaces approximately flat before transformation at an outer circumference, in which the two surfaces have a shape extended through a curved portion at a front end opposite to the opening.
In other features of the present invention, a recording head includes an ink discharging unit for discharging ink for recording, an ink container for containing air and ink supplied to the ink discharging unit, and a pressure adjustment chamber communicated with the ink container and having at least one elastic transformation body having a changeable volume according to vapor pressure to adjust the vapor pressure in the ink container and a support for supporting the elastic transformation body to the ink container, wherein the elastic transformation body includes an approximately circular opening and two surfaces approximately flat before transformation at an outer circumference, in which the two surfaces have a shape extended through a curved portion at a front end opposite to the opening.
In another features of the present invention, a recording head includes an ink container having a plurality of ink containing chambers arranged in parallel, each of which independently containing ink, an ink discharging unit for discharging ink supplied from the ink container for recording, each of the ink discharging unit corresponding to each ink containing chamber, and a pressure adjustment device installed corresponding to each ink containing chamber for adjusting pressure in the ink container, wherein the pressure adjustment device is arranged over upper portions of at least two ink containers, and the pressure adjustment device includes a plurality of elastic transformation bodies arranged to an arrangement direction of the ink containing chambers and a direction crossing the arrangement direction.